The present invention relates generally to pump control systems. More particularly, the present invention relates to synchronizing pistons in linear pumps systems.
Linear pumps include a piston that reciprocates in a housing to push fluid through the housing. Conventional linear pumps draw fluid into the housing on a backward stroke and push the fluid out of the housing on a forward stroke. Valves are used to prevent backflow through the pump. The valves can also be configured to draw in fluid and pump fluid on opposite sides of the piston during each of the backward stroke and forward stroke in order to provide a steady flow of fluid from the pump. Furthermore, typical linear pump systems utilize two linear pumps of the same construction. For example, a resin material and a catalyst material are simultaneously pumped to a mixing head of a dispensing unit. Such systems require precisely metered flow so that the proper mixture of resin and catalyst is always obtained. Mixing of the two materials produces a chemical reaction that begins a solidification process resulting in a hardened material after full curing. The resin and catalyst are not always dispensed in a 1:1 ratio such that the speeds of the pumps are the same, assuming the pumps are mechanically identical. For example, typically a 2:1 dispense ratio is used where a first pump operates the piston at speeds twice as fast as a second pump.
It is desirable that the pumps maintain synchronization such that the mix ratio is maintained. In order to do so, is necessary that the pumps reverse direction at the same time while maintaining the same speed ratio, which results in one piston using a longer stroke length than the other. Synchronization of the pumps drifts during typical operation of the linear pump system for various reasons. For example, the speeds of the pumps need to be adjusted slightly between forward strokes and backward strokes due to small differences between the effective piston surface areas in each direction. When the pistons are not properly synchronized, excessive piston reversals degrade component quality and increase pump wear. There is, therefore, a need for maintaining synchronization between pumps in linear pump systems.